Sept. 15, 2008 -- Gastric bypass surgery may be less successful for patients with diabetes and patients with a larger stomach pouch size, say researchers from the University of California, San Francisco.
The researchers examined data from 310 patients who underwent gastric bypass surgery at the University of California, San Francisco, Medical Center between 2003 and 2006.
Gastric bypass surgery is a common surgical treatment in North America to treat obesity. During the procedure, a surgeon reduces the size of a person's stomach to create a smaller pouch. This allows a person to feel full sooner. The pouch is then connected to a lower section of the small intestine, bypassing part of the small intestine, to limit the calories and nutrients the body can absorb.
"When performed in high-volume centers and with a low rate of complications, gastric bypass provides sustained and meaningful weight loss, significant improvement in quality of life, improvement or resolution of obesity-associated comorbidities and extended life span," the researchers wrote.
Even so, 5% to 15 % of patients do not lose a successful amount of weight.
To understand why, the researchers observed the study's participants for 12 months following their surgery. They examined variables that could affect a patient's ability to lose a successful amount of weight, including older age, gender, greater initial weight and BMI, race, marital status, insurance status, the presence of type 2 diabetes, and larger pouch size.
Poor weight loss was defined as losing 40% or less of the excess body weight 12 months after the surgery and good weight loss as losing more than 40% of the excess weight.
Before the surgery, their average body mass index (BMI) was 52. One year later, it was 33.9 on average. Thirty-eight of these patients (12.3%) had poor weight loss with a final average BMI of 43.8. The 87.7% of participants who had successful weight loss had an average BMI of 32.5.
After taking into account many variables, the researchers found that having diabetes, or a larger stomach pouch were linked to higher odds for poor weight loss after gastric bypass surgery. When they looked specifically at patients with diabetes, they found that poor weight loss was more strongly linked to those who were taking insulin compared to patients without diabetes.
The reasoning is that people with diabetes may be taking insulin or some other type 2 diabetes drug that affects weight loss after surgery. For example, these patients may also increase their caloric intake to offset episodes of low blood sugar.
Also, one of the most important aspects of gastric bypass surgery is making the stomach pouch smaller, because it limits a person's ability to overeat. Yet, many surgeons estimate pouch size rather than using a sizing balloon, a tool used to precisely measure the gastric pouch, the researchers say.
"We conclude that gastric bypass provides good or excellent weight loss for most patients," they continued. "However, diabetes and larger pouch size are independently associated with poor weight loss after gastric bypass. Changes in the use of diabetes medications may reduce the risk of poor weight loss among diabetics undergoing gastric bypass. Detailed attention to the creation of a small gastric pouch is essential for achieving the best results."